The inventions described below relate to treatments for pulmonary hypertension and vascular surgery. Chronic obstructive pulmonary disease (COPD), chronic hypoxia, hypertension, and left ventricular hypertrophy and pulmonary hypertension are diseases of the cardiopulmonary system. Chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphysema, is a slowly progressive lung disease caused primarily by smoking. In COPD, the lungs are damaged and the airways are partly obstructed, making it difficult to breath and leading to a gradual loss of lung function. Symptoms of COPD include chronic cough, excessive sputum production, low blood oxygen levels and severe disabling shortness of breath. COPD represents the fourth leading cause of death in the United States. Chronic hypoxia (reduction of oxygen supply to the body despite adequate blood flow through the body), hypertension, and left ventricular hypertrophy are related conditions which may be symptomatic of COPD or coincident with COPD.
These serious conditions affect many people, and the primary treatments are merely ameliorative. The primary treatments for COPD include avoidance of irritants such as tobacco smoke and breathing supplemental oxygen. In advanced cases of COPD, lung reduction surgery is sometimes performed, but it is not clear that it helps. There is no known cure for COPD.
An aortocaval fistula (ACF) is a rare clinical condition that can be either spontaneous (80% of the cases), related to abdominal aortic aneurysm, or the result of some trauma such as lumbar disk surgery. It is currently seen as a defect that should be cured with surgery and, possibly, stent-graft implantation in the aorta.
Contrary to this understanding, an intentionally formed aortocaval fistula appears to be a viable treatment for COPD. Recently, in our co-pending U.S. patent application Ser. No. 10/820,169 filed Apr. 6, 2004, entitled Implantable Arteriovenous Shunt Device and listing John L. Faul, Toshihiko Nishimura, Peter N. Kao & Ronald G. Pearl as inventors (the entirety of which is hereby incorporated by reference), we propose creation of an artificial aortocaval fistula as a treatment for COPD, and we disclose the method of creating the fistula and an implantable shunt for maintaining the aortocaval fistula.
Shunts or stents for connecting blood vessels have been proposed for the treatment of coronary artery disease. Makower, Device, System and Method for Interstitial Transvascular Intervention, U.S. Pat. No. 6,746,464 (Jun. 8, 2004) (filed Oct. 28, 1998) discloses a stent with a short tubular section spanning the thickness of a coronary artery and an adjacent parallel coronary vein. This stent includes “clovers” on either end of the stent, and these clovers fold radially outwardly to obstruct movement of the stent through the vessel walls. Two clovers on the proximal end of the stent are orthogonal (relative to the radial cross section of the stent) to two clovers on the distal end of the stent, and the interconnecting wires are parallel to the longitudinal axis of the device.